ENGINEERING LOGIC DIAGRAMSDOE-HDBK-1016/2-93Logic DiagramsPR-05Page 6Rev. 0Figure 5 COINCIDENCE Gate Figure 6 EXCLUSIVE OR and EXCLUSIVE NOR GatesThe COINCIDENCE gate behaves like an AND gateexcept that only a specific number of the total numberof inputs needs to be on for the gate's output to be on.The symbol for a COINCIDENCE gate is shown inFigure 5. The fraction in the logic symbol indicates thatthe AND gate is a COINCIDENCE gate. Thenumerator of the fraction indicates the number of inputsthat must be on for the gate to be on. The denominatorstates the total number of inputs to the gate.Two variations of the OR gate are the EXCLUSIVEOR and its opposite, the EXCLUSIVE NOR. TheEXCLUSIVE OR and the EXCLUSIVE NOR aresymbolized by adding a line on the back of the standardOR or NOR gate's symbol, as illustrated in Figure 6. EXCLUSIVE OR - provides an output (on) when only one of the inputs is on. Anyother combination results in no output (off).EXCLUSIVE NOR - is the opposite (NOT) of an EXCLUSIVE OR gate's output. Itprovides an output only when all inputs are on or when all inputs are off.TimeDelaysWhen logic diagrams are used to represent start/stop/operate circuits, the diagrams must alsobe able to symbolize the various timing devices found in the actual circuits. There are threemajor types of timers. They are 1) the Type-One Time Delay Device, 2) the Type-Two TimeDelay Device, and 3) The Type-Three Time Delay Device.